1. Field of Invention
The present invention relates to giant magnetoresistance (xe2x80x9cGMRxe2x80x9d) transducers or read heads for reading magnetic signals from magnetic recording media, and more particularly, to current perpendicular-to-the-plane giant magnetoresistance (xe2x80x9cCPP-GMRxe2x80x9d) designs. While the invention finds particular application in conjunction with reading hard disk drives, the invention can be implemented with other magnetic storage media. Moreover, the invention can be implemented in other magnetic field detection devices as well as in other devices and environments.
2. Description of the Related Art
Giant magnetoresistance (GMR) was initially described by Baibich et al. in Physical Review Letters, Volume 61, No. 21, pp. 2472-2475 (1988) which is hereby incorporated by reference. GMR occurs when an application of an external field causes a variation in the relative orientation of the magnetizations of neighboring ferromagnetic layers. This in turn causes a change in the spin-dependent scattering of conduction electrons, thereby changing the electrical resistance of the structure. The discovery of GMR triggered a wide study of transport properties of magnetic multilayers. In most cases, the current flows-in-the plane of the layers, called CIP-MR.
Pratt et al. extended the GMR measurements to the case where the current flows perpendicular-to-the-plane, called CPP-MR as described in Physical Review Letters, Volume 66, pp. 3060 (1991) which is hereby incorporated by reference. In general, the CPP-MR effect is several times larger than the CIP-MR effect. For MR read head applications, the CPP-MR element has to be dramatically scaled down ( less than 100 nm) because of the very small specific resistance of the MR element with the CPP configuration.
U.S. Pat. No. 5,627,704 and U.S. Pat. No. 5,668,688 (which are both hereby incorporated by reference) have described the application of CPP-MR for magnetic transducers. In both cases, a longitudinal magnetic bias means was provided as usual by permanent magnets located at the sides of the GMR structures. With longitudinal magnetic bias, the GMR structure must be a spin valve type structure in order to have good linear response in the field of small signals.
Accordingly, the present invention is directed to a current perpendicular-to-the-plane magnetoresistance read head that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a current perpendicular-to-the-plane magnetoresistance (CPP-MR) read head includes a top shield formed of magnetically shielding, electrically-conductive material, a bottom shield formed of a magnetically shielding, electrically-conductive material; and a giant magnetoresistance (GMR) structure disposed between the top shield and the bottom shield, the GMR structure being in electrical contact with the top and bottom shield. A first current flows from one of the top and bottom shields through the GMR structure to the other one of the top and bottom shields. A metal pillar is electrically connected to one of the top and bottom shields. The metal pillar carries a second current and is disposed such that the second current flows in a direction generally perpendicular-to-the-plane of the GMR structure.
In another aspect, a current perpendicular-to-the-plane magnetoresistance (CPP-MR) read head includes a pair of magnetic shields defining a read gap; a giant magnetoresistive (GMR) pillar disposed between the pair of magnetic shields in the read gap, the pair of magnetic shields serving as electrical contacts for the GMR pillar; and a nonmagnetic metal pillar electrically connected to one shield of the pair of magnetic shields, the metal pillar disposed parallel to the GMR pillar and separated from the GMR pillar, wherein sense current flows through the GMR pillar according to a perpendicular-to-the-plane model such that the sense current also flows through the metal pillar to provide a magnetic bias.
In another aspect, a method of magnetically biasing a current perpendicular-to-the-plane magnetoresistance (CPP-MR) read head is provided. A current is generated in a GMR structure in a CPP-MR read head. The read head is magnetically biased using the current.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.